Ship&#39;s hull



L. COSTA SHIP'S HULL Aug. 23, 1966 2 Sheets-Sheet 1 Filed June 9. 1964L. COSTA SHIP'S HULL Aug. 23, 1966 Filed June 9. 1964 2 Sheets-Sheet 2United States Patent 3,267,896 SHIPS HULL Leo Costa, Vienna, Austria,assignor to Maierform Holding S.A., Geneva, Switzerland Filed June 9,1964, Ser- No. 373,670 7 Claims. (Cl. 114-56) This invention relates toa ships hull and, more particularly, to a shape of bulbous bow sometimescalled a club foot. The invention is particularly suitable for fastships of every type having a lower Froude number speed-length ratio ofabout 0.25 (metric).

It is the chief object of this invention to provide a bulbous nose ofthe type mentioned, having its largest diameter in the load waterlinewith a wedge type swelling of the bulb which steadily decreases in thedirection of the keel aft, and extends upwardly above the load waterline to a distance of at least one fourth the draft or depth of theimmersed portion of the hull.

Another object is to provide a hull wherein excessive pitching isobviated by a stem of improved form having a downwardlyevenly-decreasing cross section of the bulb of the bow.

Still another object is to avoid and obviate the drawbacks ofconventional bulbous bow constructions.

Yet another object is to provide a bulbous ships bow wherein the crosssections of the several waterlines at the stern are preferably in theform of circular or conic section arcs.

Another object is to provide a bulbous bow as aforesaid wherein eachwaterline extending from the greatest horizontal transverse dimension ofthe bulb, first passes outwardly of the corresponding waterline of aconventional form of hull, and with increasing distances aft of the bulbgradually approaches, intersects, passes within, and again graduallyapproaches the aforesaid corresponding waterline of a conventional formof hull. In some cases, however, the respective waterlines of theinvention may not actually intersect the aforesaid conventional loadwaterline but merely approach the same with increasing distances aftfrom the bulb or stem and merge into the conventional line at a framesuch as 18 depicted upon the drawings. The constriction thus formedrearwardly of the stem portion, designated as a pocket, is, of course,greatest in and above the load waterline and becomes less pronouncedwith waterlines of increasing distance below load waterlines.

Yet another object is to provide a bulbous bow of the type aforesaidwhich results in appreciable savings in power required for propulsion atany given speed, results in decreased bow waves, decreases pitching byincreasing buoyancy at and along vertical transverse sections adjacentthe fore part of the bow, and improves the form of the entire waveprofile along the sides of the hull.

Other objects and advantages will be apparent to those skilled in theart, after a study of the following detailed description in connectionwith the accompanying drawing.

In the drawing:

FIG. 1 is a vertical longitudinal view of the profile of the stem andbow portions of a hull embodying the invention and showing the contoursat various water lines WLO to WL6, as compared to the correspondingprofiles of a conventionally shaped hull;

FIG. 2 is a view showing half-section profiles in vertical transverseplanes numbered in correspondence with those identified upon FIG. 1;

FIG. 3 shows to a greatly enlarged scale, the profile in and along theconstruction waterline, of the bow of a ship embodying the invention,with the corresponding profile of a ship having a bow of conventional orusual 3,267,395 Patented August 23, 1966 form shown in dotted line andthe largest to the bulbous stern shown in dot-dash line;

FIGS. 4, 5 and 6 each correspond to FIGS. 1, 2 and 3, respectively, butshow a somewhat diiferent shape of stem portion, both in side elevationand in waterline sections.

Referring in detail to FIGS. 1, 2, and 3, S indicates the stem contourand CWL the construction waterline. Waterline planes WLO through WL6 areidentified as straight horizontal lines and at each is shown by a solidline, the half-profile of the hull at that line, starting from a pointdefined by the intersection of each horizontal line with the stemline.Also, starting from each of the aforesaid points as shown, in dottedlines, the corresponding profile of a hull of conventional or prior artform. At each waterline or horizontal plane the dotdash line is atangent to the conic section or other are defining the bulbous stem, andextending rearwardly and outwardly from the respective terminal pointsA, B, C, D, E, etc. thereof.

Referring more particularly to the enlarged-scale view of FIG. 3, thereis shown in solid line, the profile of a hull embodying the invention,with the corresponding profile of a hull of conventional form shown indotted lines From this figure it is noted that, starting from itsintersection with the stem line and extending to point A, the CWL lineof the hull embodying the invention, has the form of a portion of anellipse so that point A lies outwardly of the corresponding point of ahull of conventional design. From a point of tangency at A, the CWL ofthe invention gradually approaches the convention dotted line form,crosses it, and then fairs outwardly to again approach and eventually togenerally coincide with the dotted-line construction. Still referring toFIG. 3, dimension .2; identifies the greatest or maximumhorizontally-inward departure of the CWL of the invention from theconventional dotted-line form. As previously explained, the dot-dashline 2. identifies a straight line tangent to the ellipse at point A, sothat the dimension f is the offset inwardly of the point of maximumdeparture of the CWL of the invention from this line of tangency.

FIG. 3 is thus illustrative of the corresponding solid, dotted anddot-dash lines indicated upon FIG. 1 for each of the Waterlines 0through 6, and the corresponding e and f distances described in thepreceding paragraph. Reverting to FIG. 1, the dimension d for example,is the horizontal distance between the two term-i-' nal points A,intersected on the elliptical portion of the stern b-y CWL (WL4). Thepoints on water lines WL3, WL2, WL1, and WL /2 corresponding the pointA, FIGS. 1 and 3, are identified respectively at B, C, D and E, and ineach case locate or identify the thickest part, or part of greatestdiameter of the stem bulb at the corresponding water line. Inspection ofFIG. 1 shows that these distances d d etc. progressive increase from thelowermost water line plane, upwardly. A faired line L, FlGS. 1 and 2,passing through the aforesaid points A through E, etc., is generallyparallel to stem line S, as is clear from inspection of FIG. 1. Fromthis figure it is also noted that line L extends uniformly and fairlyfrom the uppermost water line almost to merger'with keel line K.

From FIG. 2 it is noted that a projection of line L onto a transversevertical plane is essentially straight from its intersection with WLl toits intersection with uppermost WL6, and departs only slightly upwardlyand outwardly from parallelism with the vertical longitudinal medianplane of the hull. This feature is characteristic of all embodiments ofthe invention.

The largest dimension by which the waterline depart-s inwardly, that is,toward the vertical longitudinal median ice plane of the hull, isidentified at e and occurs at the normal or load water line. As clearlyshown upon FIG. 1, thus e dimension uniformly decreases at subsequentlower Water lines. Likewise distance f previously explained, is amaximum and other f distances such as f f etc. progressively decrease. Afair curve B, FIG. 1, connecting all points f f etc. is simple, andshows that there is no local swelling in the bow between frames 18 and19 identified upon the figures. As seen upon FIG. 2, the projection E ofline B, onto a transverse vertical plane is also essentially straightover the main portion of its length.

The form of the invention shown upon FIGS. 4, 5 and 6 correspondsgenerally to that depicted upon FIGS. 1, 2 and 3. Since all lines areidentified by referenc characters corresponding to those of FIGS. 1, 2and 3, and since the significance of the solid, dotted and dot-dashlines are the same as in the form previously described, it is deemedunnecessary to explain FIGS. 4, 5, and 6 in detail.

However, unlike the species of FIGS. 1, 2 and 3, the cross sectionalform of the stem in water line planes is parabolic as shown more clearlyupon FIG. 6. The particular conic section selected is not critical andmay be any section from circular to parabolic or even oval, and inparticular cases it may be formed with a rather gentle entrance.

[In all cases the starting point for establishing the dimensions d detc. is given by the range of Froudes numbers for which the ship of thepresent invention is to be used. As shown upon FIG. 4, the stem line isextended deadwood-like into the generally triangular space formedbetween the forward plumb line P, keel li-ne K and stem line S. In thisway the superiority of a bow constructed according to the invention canbe further enhanced, particularly for Froude numbers between 0.25 and0.30 and above.

The bulbous bow constructed in accordance with the invention utilizes tobetter advantage the trim efiect of the hull, in cooperation with thepocket formed as the result of the construction between the stem andframe 19. This coaction decreases the bow wave at any given speed, overthat of a like hull of conventional form, essentially with respect toits mass, i.e., more in its breadth than in its height. The improvedhull form also has a favorable bearing on the entire wave profile alongthe side of the hull. That is to say, successive wave crests :becornelower and the wave troughs flatter, thus decreassing the power requiredfor propulsion. A total saving of from 4 to 6 percent in propellingenergy is thus made possible.

The foregoing disclosure relates directly to the embodiments shown anddescribed and numerous modifications or alternations are possiblewithout departing from the spirit and scope of the invention pointed outby the appended claims.

I claim:

1. A bow of a ships hull comprising a stem provided with a swelling, thehorizontal cross-sections of said swelling having the shape of a sectionof a cone, the diameters of said cone sections decreasing in size fromthe load. waterline to the keel, said swelling extending above said loadwaterline into the dead work of the ships hull to a height correspondingat least to one fourth of the draught.

2. A ships h-ull as claimed in claim 1 comprising pockets formed behindthe swelling by curves merging the swelling into the waterlines.

3. A ships hull as claimed in claim 2 wherein said pocket-formingwaterlines first intersect, and then merge into, the normal basewaterlines.

4. In a ships hull having a vertical longitudinal median plane ofsymmetry, a bow having a stem swelling in each of a plurality ofhorizontal vertically-spaced planes normal to said median plane, thecross-section of the swelling in said planes being in the outline formof substantially a half of a section of a cone having its apex on thestem line of said bow and its terminals at two points symmetricallydisposed with respect to and upon opposite sides of said median planerearwardly of said stem line, the respective tangents of said conicsection at each said point diverging rearwardly and outwardly inrespective ones of said horizontal planes, symmetrically with respect toand upon opposite sides of said median plane, the side profiles of saidbow in each said horizontal plane coinciding with said tangents at saidpoints, then curving inwardly and rearwardly, then outwardly andrearwardly, in fair curves, each with respect to its said tangent, saidhorizontal planes extending from substantially the keel line of saidhull to a distance at least one-fourth of the draft above the load waterline thereof.

5. In a ships hull having a vertical longitudinal median plane ofsymmetry, a bow having a stem swelling in cross section in each of aplurality of parallel horizontal waterline planes normal to said medianplane, each said cross section being in outline substantially one-halfof a section of a cone with its apex on the stem line of said how andits terminals at the point symmetrically disposed with respect to andupon opposite sides of said median plane rearwardly of said stem line,the respective tangent lines to said conic section at each said pointdiverging rearwardly and outwardly each in its respective waterlineplane, symmetrically with respect to, and upon opposite sides of saidmedian plane, the side profiles of said bow in each said waterline planeconnecting with the corresponding tangent line at a respective one ofsaid points, then curving inwardly and rearwardly, then outwardly andrearwardly in fair curves, each with respect to its said tangent line,said planes extending from substantially the keel line of the hull to avertical distance above the load waterline at least one-fourth of thedraft of said hull, the distance of separation of said points in eachrespective waterline plane decreasing uniformly in sequential planesfrom the construction waterline plane to therebelow, a fair curveconnecting all said points on one side of said median plane beingessentially parallel to the stem line of said bow, the projection ofsaid line upon a transverse vertical plane normal to said median planebeing essentially a straight line diverging upwardly and out- Wardly ata small acute angle from said median plane, the maximum separation pointof the profile line of the bow, inwardly from the corresponding tangentline being in said construction line plane and decreasing uniformly insequential planes there-below, all said points of maximum separation onthe corresponding side of said median plane conjointly defining a secondfair curve, the projections of said second fair curve onto said medianplane and onto a transverse vertical plane normal thereto, beingessentially straight lines diverging from said respective planesupwardly and forwardly and upwardly and outwardly both at small acuteangles with Vertical.

6. The hull of claim 5, said cone section being elliptical.

7. The hull of claim 5, said cone section being parabolic.

References Cited by the Examiner UNITED STATES PATENTS 3,090,338 5/1966' Costanzi 114-56 3,180,299 4/ 1965 lnlli 1l4--56 FOREIGN PATENTS449,417 6/ 193 6 Great Britain. 109,257 12/ 1943- Sweden.

MILTON BUCHLER, Primary Examiner. T. M. BLIX, Assistant Examiner.

1. A BOW OF SHIP''S HULL COMPRISING A STEM PROVIDED WITH A SWELLING, THEHORIZONTAL CORSS-SECTIONS OF SAID SWELLING HAVING THE SHAPE OF A SECTIONOF A CONE, THE DIAMETERS OF SAID CONE SECTIONS DECREASING IN SIZE FROMTHE LOAD, WATERLINE TO THE KEEL, SAID SWELLING EXTENDING ABOVE SAID LOADWATERLINE INTO THE DEAD WORK OF THE SHIP''S HULL TO A HEIGHTCORRESPONDING AT LEAST TO ONE FOURTH OF THE DRAUGHT.